Shalom Mityetu,
Just wish to add that Qaraites have differed among themselves on the
issue of when a new day begins. Some still hold it commences at the
end of sunset when the sky goes totally dark. Hence a difference on
when the Shabbat day begins and ends.
Even so, traditional Qaraism maintains that to be extra careful,
Shabbat should end at total darkness in any case.
Therefore the "only" controversy that remains is when Shabbat
commences.
May YHWH be with you,
Zvi